1. Field of the Invention
The present invention relates to a breaking apparatus and a breaking method for breaking a brittle material-made substrate formed with scribe lines along the scribe lines.
2. Discussion of the Related Art
In a conventional LED manufacturing process, LED chips are provided in a lattice arrangement on a circular sapphire substrate, and the substrate is scribed to form lines in a grid pattern (scribe lines) thereon for segmentation to obtain separate LED chips. The substrate is broken along the scribe lines. In Japanese Unexamined Patent Publication JP-A 2008-244222, there is disclosed a breaking apparatus designed for such an operation. FIG. 1 is a sectional view showing an example of how a substrate is to be broken. In FIG. 1, a substrate 101 has formed thereon a multiplicity of LED chips 102 arranged equidistantly, and an adhesive film 103 is bonded to the top of the substrate 101. Scribe lines 104 are formed equidistantly, each of which lies in a position midway between adjacent LED chips 102 on the substrate 101. The substrate 101 is placed on a sheet 105, and the sheet bearing the substrate 101 is further placed on a pair of blade rests 106. Above the substrate 101 is retained a blade 107 for free up-and-down, or vertical motion along a z axis, and under the substrate 101 is disposed a camera 108. In a breaking process, the scribe line 104 is positioned at the center of the paired blade rests 106, and the blade 107 is pressed down from directly above the scribe line 104 in the direction of the z axis to break the substrate along the scribe line 104.
FIG. 2 is a sequence diagram showing the steps of a breaking process. FIG. 3 is a time chart showing the positions of the blade in the z-axis direction, in which are also shown the step numbers described in FIG. 2. With the scribe line 104 set in a position immediately below the blade 107, breaking is started. To begin with, in step S1 of FIG. 2, the blade 107 is moved downward from a position of 0.00 mm. Even after the front end of the blade 107 is brought into contact with the adhesive film 103 on the top of the substrate, the blade 107 is further pressed down to a position of −0.30 mm while decreasing the speed of downward motion to break the substrate (step S2). After the completion of breaking, in step S3, the blade 107 is raised for return to its original position, namely the position of 0.00 mm. Subsequently, in step S4, the substrate 101 is moved in the direction of a y axis shown in FIG. 1 until the following scribe line is set in position. Given that the distance of travel of the substrate corresponds to the pitch of scribe lines drawn side by side, then the following scribe line is situated substantially immediately below the blade 107 after the travel. However, since the substrate undergoes a small amount of displacement because of the breaking process, it follows that the following scribe line is not exactly situated immediately below the blade 107. In view of this, after the travel, an image of the substrate 101 is taken from below by the camera 108 in a region between the blade rests 106 (step S5). Then, image processing is performed to detect the position of the following scribe line (step S6), and a minute correction is made to the position of the substrate 101 so that the scribe line can be situated immediately below the blade 107 in the y-axis direction (step S7). After the completion of the positional correction, the procedure returns to step S1 to repeat the same process steps.
Thus, according to the conventional breaking method, since the substrate undergoes a small amount of displacement when the blade makes contact with the substrate for breaking, it is necessary to make a fine adjustment of the position of the substrate every time breaking is carried out to correct the displacement. However, an image of the substrate is taken by the camera after the substrate is moved until the following scribe line to be cut for breaking is set in position, and also image processing is performed to detect the position of the scribe line. That is, much time is required for the process steps including the image processing with a consequent undesirable increase in breaking time. As another problem, if the angle of the substrate is deviated, it will be difficult to achieve angular correction adequately.